With regard to a recording apparatus for recording conventional video signals on a recording medium, there is disclosed an apparatus which records time map information including at least one of a recording address and reproduction time information of each data unit while the video signals are recorded on a data unit basis (see, for example, Japanese Patent No. 3028517, pages 7 to 9, FIG. 9 and Japanese Patent Laid-open Application No. 2001-103428, pages 13 and 15). The time map information allows one to have random access to the recorded video signals.
As a method for recording video signals onto a DVD-RAM medium, there is provided a DVD video recording standard (hereinafter, referred to as a ‘DVD-VR standard’). The DVD-VR standard requires that video signals are recorded in units of video object units (hereinafter, referred to as ‘VOBUs’); and time map information of each VOBU (VOBU map information) is recorded. A reproduction time length of each VOBU is required to be within a range from 0.4 to 1.0 seconds.
In case of recording video signals on a DVD-R medium, recording is carried out in accordance with a DVD-Video standard. The DVD-Video standard also defines VOBUs; and also requires that a reproduction time length of each VOBU is set to be within a range from 0.4 to 1.0 seconds same as the DVD-VR standard.
Further, digital image signals are generally recorded as a video stream derived by compressing data in compliance with an MPEG encoding standard. The MPEG encoding standard defines the intra-frame encoding (I-pictures), the predictive-encoding (P-pictures) and the bidirectionally predictive-encoding (B-pictures). Herein, a frame group led by an I-picture is called the Group of pictures (hereinafter, referred to as ‘GOPs’). In order to reproduce the video stream by random-access, reproduction starts from the I-picture that can be independently reproduced. Namely, access on a GOP unit basis can be realized.
Meanwhile, since the DVD-VR standard requires that each VOBU includes at least one GOP, access on a VOBU unit basis can be also realized by using VOBU map information. Further, even while the VOBU map information is recorded on a recording medium, during a reproduction process, the VOBU map information is transferred to an internal memory so that it can be read out from the memory during random-access. For the random-access, a reproduction time length of each VOBU is set to be about 0.5 seconds.
Meanwhile, a DVD recorder can record up to 2 hours of video signals on a 4.7 GB DVD-RAM medium in a standard mode (hereinafter, referred to as ‘SP mode’). Further, it can record up to 4 hours of video signals in a long play mode (LP mode). Those recording modes can be realized by controlling a compression rate (bit rate) in compliance with MPEG specifications. Since the bit rate in the SP mode is 5 Mbps and that in the LP mode is 2.5 Mbps, a recording of video signals in a long play mode can be realized by lowering the bit rate.
However, although the long play recording mode can be realized by lowering the bit rate in case of MPEG encoding in such as DVDs, there has been a problem that a memory size for recording the time map information increases since the longer the recorded video signals are, the larger a total size of the time map information becomes.
For example, when a data unit is 0.5 seconds long and a time information size of each data unit is set to be 3 bytes, the relationship between the recording time and the total data size of the time map information is shown in Table 1.
TABLE 1Recording time modeData size of[hours]time map information [bytes]243,200486,4008172,80012259,20016345,600
For example, a 200 Kbytes memory is sufficient to record up to 8 hours of video signals whereas a memory of at least 345 Kbytes is required to record up to 16 hours of video signals.
On the other hand, if a size of a time map information storage memory installed in the recording apparatus is 200 Kbytes, recording of the video signals can be performed only for about 8 hours to prevent the time map information storage memory from being overflowed.
Further, there has been a problem that when reproducing video signals recorded in a long play mode on a recording medium, the video signals cannot be fully reproduced due to an overflow in the time map information storage memory.
Furthermore, since recording formats vary depending on types of recording media, a memory size for storing the time map information can be varied accordingly, thereby resulting in a problem that a maximum time for recording varies depending on the types of the recording media.
The present invention is contrived on the basis of the aforementioned problems and it is, therefore, an object of the present invention to provide a recording apparatus and method capable of recording of video signals in a long play mode without overflowing a memory of time map information, a reproduction apparatus and method, and a recording medium thereof.